Question

In a polygon no three diagonals are concurrent. If the total number of points of intersection of diagonals interior to the polygon be 70 then the number of diagonals of the polygon is

• A. 20
• B. 28
• C. 8
• D. 36

Answer 1

The correct option is A 20

${}^n{C}_4=70\Rightarrow n=8$ $\therefore$ no.q diagonals of polygon $\frac{n(n-3)}{2}$